1. Field of the Invention
The present invention relates to a novel polyimide, and particularly relates to a polyimide having a high heat-resistance and good processability. 2. Description of the Prior Art
A polyimide obtained by reacting tetracarboxylic acid dianhydride and diamine compound has conventionally been used in various fields due to excellent properties and good thermal-resistance, and is expected to be applied to various fields where high-temperature stability is required.
Many kinds of polymide which have conventionally been developed exhibit excellent properties. However, polyimide having excellent thermal-resistance shows poor processability while the resin developed for improving processability is poor in resistance to heat and solvents. Thus advantageous characteristics and drawbacks have been found in combination.
For example, polyimide consisting of a fundamental skeleton represented by the formula (II): ##STR2## (Trade Mark; Kapton and Vespel, the products of E.I. Du Pont De Nemours & Co. Inc.) has no definite glass transition temperature and is excellent in high-temperature resistance. The polyimide, however, is difficult to process as a molding material and must be processed by specific methods such as sinter molding. The polyimide has also high water absorption which gives adverse effects on dimensional stability, insulative property and solder heat resistance of electric and electronic parts.
Polyetherimide consisting of a fundamental skeleton represented by the formula (III): ##STR3## (Trade Mark; ULTEM, a product of General Electric Co.) is a resin having excellent processability. The resin, however, has a relatively low glass transition temperature of 217.degree. C. and is soluble in halogenated hydrocarbons such as methylene chloride. Hence, the resin is unsatisfactory in view of resistance to high temperature and solvents.